Method and device for automatic controlling of the deceleration device of a vehicle

ABSTRACT

A method and a device are described for controlling deceleration devices of a vehicle during a braking operation, in particular a vehicle which is equipped with a sensor for adaptive cruise control. During the braking operation, risk dimensions are determined on the basis of driving dynamics models, which are individualized by signals of the surrounding-field sensor system. A first risk dimension is precalculated for the case of continued deceleration and a second risk dimension is precalculated for the case of unbraked further movement of the vehicle. Through the comparison of the two risk dimensions, it is decided whether the automatic vehicle deceleration is to be maintained or whether the braking is to be canceled before the vehicle is brought to a standstill.

FIELD OF THE INVENTION

[0001] A method and a device are proposed for controlling decelerationdevices of a vehicle during a braking operation, in particular of avehicle which is equipped with a sensor for adaptive cruise control.During the braking operation, risk dimensions are determined on thebasis of driving dynamics models, which are individualized on the basisof signals from the surrounding-field sensor system, as well as on thebasis the characteristic driver behavior to be expected, which has beenobtained through analysis of the prior driver reactions. A first riskdimension is precalculated for the case of continued deceleration and asecond risk dimension is precalculated for the case of unbraked furthermovement of the vehicle. By comparing the two risk dimensions, it isdecided whether the automatic vehicle deceleration is to be maintainedor whether the braking is to be canceled before the vehicle is broughtto a standstill.

BACKGROUND INFORMATION

[0002] Cruise controls which reduce the set speed using a ranging sensorwhen a slower vehicle has been detected driving in front of theparticular vehicle are known. These types of systems have beendistributed under the name “adaptive cruise control” (ACC). A system ofthis type is described in the article “Adaptive Cruise Control SystemAspects and Development Trends” by Winner et al. (SAE paper 96 1010,International Congress and Exposition, Detroit, Feb. 26-29, 1996).Systems of this type have been planned until now as comfort systems, dueto which the maximum deceleration performance of these systems isinsufficient to delay imminent collisions with vehicles driving infront.

[0003] German Patent 197 50 913 describes an automatic brake controlsystem for motor vehicles which is capable of detecting obstacles andbraking the particular vehicle to a standstill in the event of animminent collision. This is done using an obstacle detection device fordetecting an obstacle in front of the vehicle, a stop decision devicefor deciding whether the vehicle has essentially been stopped, a brakingforce determination device for determining a braking force to keep thevehicle stopped, a braking force control device, a travel resumptiondecision device, and a release device for releasing the braking force.This system is distinguished in that a vehicle may be automaticallybraked to a standstill. However, aborting the deceleration during thebraking intervention is mentioned neither in this publication nor in anyother known publication.

ESSENCE AND ADVANTAGES OF THE INVENTION

[0004] The essence of the present invention is to be able toautomatically brake vehicles, in particular vehicles having adaptivecruise control, and at the same time to implement the braking so thatthe occupants are endangered as little as possible. This is done throughthe features of the independent claims. Advantageous refinements aredescribed in the subclaims. The decision of whether a deceleration foravoiding collisions is to be maintained or aborted is made on the basisof a comparison of two calculated risk dimensions. A first riskdimension, which represents the risk of the particular vehicle in theevent of continued deceleration, and a second risk dimension, whichrepresents the risk of the vehicle if the brakes are opened during thedeceleration, are provided. During a braking operation, it is possiblethat the vehicle will begin to rotate about its vertical axis due toinsufficient road-surface adhesion or if the steerable front wheels havebeen turned during braking. If the limit of adhesion of the tires on theroadway is reached again, these types of situations may lead to theparticular vehicle becoming uncontrollable and collisions occurring withstationary or moving obstacles. In order to avoid this, it iscontinuously checked during the braking maneuver to avoid a collisionwhether it is more favorable in terms of safety to release the brakesand steer the vehicle in a controlled way around the obstacle or whetherit is more favorable to maintain the emergency braking even though thebrake pedal has been released by the driver and to prevent uncontrolledbreakaway of the vehicle.

[0005] Furthermore, it is advantageous that the automatic braking iseither automatically initiated braking or braking which is initiated bythe driver, but is performed automatically. Both possibilities share thefeature, however, that a strong deceleration to avoid a collision or toreduce the collision speed occurs during braking, whose decelerationcorresponds to approximately the maximum possible vehicle deceleration.

[0006] Furthermore, it is advantageous that the deceleration means aredeactivated during a braking operation if the comparison of the riskdimensions shows that the first risk dimension is greater than thesecond risk dimension. If the first risk dimension is smaller than thesecond risk dimension, the braking operation is continued even if thedriver deactivates the brake pedal during the braking operation.

[0007] The first and the second risk dimensions are advantageouslydetermined using precalculated movement trajectories of the detectedobstacles and of the particular vehicle. For precalculating the movementtrajectories, the positions and the movements of the particular vehicleand the stationary and moving obstacles in the area surrounding of thevehicle are taken into consideration using driving dynamics models andthe characteristic driver behavior to be expected.

[0008] Furthermore, it is advantageous that the characteristic drivingbehavior of the driver is taken into consideration in establishing theparticular situation. In this case, it is taken into consideration howthe driver executes steering, acceleration, and braking activities,whether they are rather slow and done as weakly as possible or abruptand violent. It may also be taken into consideration which dynamicresponse the driver uses to accelerate, decelerate, or steer the vehicleon average.

[0009] Advantageously, signals from at least one of the followingsensors are processed to detect the surrounding-field situation and theparticular vehicle situation: yaw rate sensor, radar sensor, lidarsensor, video sensor, wheel speed sensor, steering angle sensor,accelerator pedal sensor, brake pedal sensor, and mass inertia sensor.It is not necessary according to the present invention for all of thesensor signals listed to be processed; however, it is also possible thatfurther signals of sensors which detect the vehicle surroundings or theparticular vehicle movement are additionally taken into consideration.

[0010] The controller of the deceleration means advantageouslydifferentiates at least three states, the controller being able toassume precisely one of the following states at a point in time:

[0011] no deceleration of the vehicle and no deceleration preparation,

[0012] no deceleration of the vehicle, but preparation of thedeceleration means by prefilling the braking system and applying thebrake linings to the brake disks, and

[0013] maximum possible deceleration of the vehicle.

[0014] Furthermore, it is advantageous if the controller of thedeceleration means has at least four states, in particular, thatprecisely one of the following states is assumed at a point in time:

[0015] no deceleration of the vehicle and no deceleration preparation,

[0016] no deceleration of the vehicle, but preparation of thedeceleration means by prefilling the braking system and applying thebrake linings to the brake disks,

[0017] deceleration of the vehicle which lies below the maximum possibledeceleration of the vehicle, and

[0018] maximum possible deceleration of the vehicle.

[0019] The method described is advantageously executed by a device whichprovides detection means for detecting the surrounding field situation,the situation of the particular vehicle, and the driver activities;these may be supplied to an analysis device, in which probable movementtrajectories of the particular vehicle and the stationary and movingobstacles detected in the surrounding area may be established usingdriving dynamics models, a first and a second risk dimension areestablished from these movement trajectories, and means for deceleratingthe vehicle may be activated or deactivated as a function of the resultof the comparison of the first and the second risk dimensions.

[0020] The implementation of the method according to the presentinvention in the form of a control element which is provided for acontrol unit, in particular a control unit for an adaptive cruisecontrol, is of particular significance. In this case, a program isstored on the control element which is executable on a computing device,in particular on a microprocessor or ASIC, and is capable of executingthe method according to the present invention. The present invention isthus be implemented in this case by a program stored on the controlelement, so that this control element provided with the programrepresents the present invention in the same way as the method which theprogram is capable of executing. In particular, an electronic memorymedium may be used as a control element, for example, a “read-onlymemory” or an “ASIC.”

[0021] Further features, possible applications, and advantages of thepresent invention result from the following description of exemplaryembodiments of the present invention, which are illustrated in thefigures of the drawing. In this case, all features described orillustrated form the object of the present invention, alone or in anycombination, regardless of their wording in the patent claims or whatthey are based on and regardless of their formulation and representationin the description and the drawing.

DRAWING

[0022] In the following, exemplary embodiments of the present inventionare described on the basis of figures.

[0023]FIG. 1 shows a state diagram for the controller of thedeceleration devices having three operating states,

[0024]FIG. 2 shows a state diagram for the controller of the vehicledeceleration devices having four operating states,

[0025]FIG. 3 shows a sketch of a driving situation in which the methodaccording to the present invention is used,

[0026]FIG. 4 shows a further sketch of a traffic situation in which themethod according to the present invention is used, and

[0027]FIG. 5 show a block diagram of the device according to the presentinvention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0028]FIG. 1 shows a state transition diagram of a preferred embodimentfor the controller of the deceleration means. In FIG. 1, block 1represents the operating state in which no deceleration and nodeceleration preparation are required. This means that the brakingsystem is unpressurized and no braking intervention occurs. State block2 represents the operating state in which no deceleration of the vehicleis required, but the deceleration means are prepared for a possibleimminent deceleration. This is done by prefilling the braking system andapplying the brake linings to the brake disks without exerting pressureon them in order to be able to cause more rapid deceleration in theevent of braking. Operating state 3 in block 3 represents braking of thevehicle using a maximum possible deceleration, in order to avoid animminent collision or to mitigate a collision which may no longer beavoidable. Transition 4 from operating state 1 into operating state 2occurs automatically when a sensor signal determines a driving state inwhich an imminent collision must be expected. This is advantageouslyperformed by monitoring the yaw rate or the steering angle deflection,the radar, lidar, or video sensors, or the brake pedal sensor. If asignal of this type exceeds a preselected threshold value or acombination of the signals exceeds a preselected combination ofthreshold values, the deceleration means are prepared for possibleimminent emergency braking in the way described above. If thesepreparation criteria of transition 4 no longer exist after a preselectedtime, the deceleration preparation is canceled in that the brakingsystem is made unpressurized again. This procedure corresponds totransition 5 from operating state 2 into operating state 1. Transition 6from operating state 2 into operating state 3 represents the incitationof a strong deceleration, in that the deceleration means prepared for abraking operation are activated and are operated using maximum possibledeceleration. This is done by analyzing the sensor signals supplied tothe device, in that it is recognized from one or more of these signalsthat a collision with a stationary or moving obstacle is unavoidable.Transition 7 from operating state 3 to operating state 2 embodies theaborting of a deceleration using maximum possible deceleration, brakingpreparation being maintained.

[0029] Transitions 4, 5, 6, and 7 in FIG. 1 are controlled automaticallyaccording to the present invention, in that the sensor input data isanalyzed in the way according to the present invention.

[0030]FIG. 2 describes a similar exemplary embodiment, a furtheroperating state 8 for controlling the deceleration means being providedin this exemplary embodiment. This further operating state 8 representsa deceleration of the vehicle which lies below the maximum possiblevehicle deceleration and may therefore be described as partialdeceleration. Operating states 1, 2, and 3 correspond to identicaloperating states 1, 2, and 3 from FIG. 1. Transitions 4, 5, 6, and 7between the operating states also correspond to identical transitions 4to 7 from FIG. 1. Transitions 9, 10, 11, and 12 are newly added.Transition 9 between operating state 3 and operating state 8 representsa reduction of the vehicle deceleration from approximately the maximumpossible vehicle deceleration to a partial deceleration. Transition 10represents the transition from state 8 to state 3 and embodies anincrease in the deceleration from a partial deceleration to the maximumpossible vehicle deceleration. Transition 11 from state 2 to state 8represents the initiation of a deceleration, in that the decelerationsystem prepared for braking begins actual deceleration of the vehicle,this vehicle deceleration corresponding to a deceleration which liesbelow the maximum possible vehicle deceleration. State 12 in the reversedirection represents the cancellation of a partial deceleration towardfurther movement without deceleration, but using a braking system whichis prepared for deceleration.

[0031] Operating state 8 of the state transition diagram in FIG. 2embodies decelerations which lie below the maximum possible vehicledeceleration. This means that in this state 8 a variable brake pressureis possible, which may change as it is observed over time.

[0032]FIG. 3 represents a possible traffic situation, in which themethod according to the present invention is used. A street 13 is shown,one roadway being provided in each direction. Vehicle 14, which isequipped with the device according to the present invention, moves onthis roadway. A vehicle 15 is driving ahead of this vehicle 14, and avehicle 16 is approaching in the opposite direction. In theindication-free operating state, the controller of the decelerationmeans of vehicle 14 occupies operating state 1. This means that vehicle14 follows vehicle 15. If the surrounding-field sensor system of vehicle14 recognizes that the hazard potential increases, which is caused, forexample, by strong deceleration of vehicle 15 or by the suddenappearance of an obstacle between vehicle 14 and vehicle 15, thecontroller of the deceleration means enters operating state 2. This hasthe consequence that the deceleration means are prepared for possibleimminent emergency braking, in that the braking system of the vehicle isprefilled and the brake linings are applied to the brake disks. If therisk dimension for vehicle 14 increases, two reactions are possible.Either the driver recognizes the hazard situation himself and initiatesa braking operation through a corresponding brake pedal operation, orthe driver does not recognize the risk dimension of this drivingsituation and the controller of the deceleration means automaticallyinitiates a braking operation. In the further course of these twopossible braking operations, the surrounding-field sensor systemdetermines risk dimensions, from the recognized obstacles, in thisexample vehicles 15 and 16 or a suddenly appearing obstacle betweenvehicles 14 and 15, for a continued deceleration and for an abort of thedeceleration. To determine these risk dimensions, the positions andspeeds of the obstacles are determined using the surrounding-fieldsensor system and their further movement trajectories are precalculated.In the course of the deceleration operation, it may occur that theroad-surface adhesion of the wheels of vehicle 14 loses adhesion and thevehicle begins to skid. This is indicated in the exemplary situation, asis illustrated in FIG. 3, by arrow 17, which represents a movement ofthe vehicle about its vertical axis. In this situation, the methodaccording to the present invention is to ensure that when theroad-surface adhesion of the wheels sets in again, the vehicle does notmove further onto the opposite roadway. For this purpose, it isnecessary not to abort the braking for avoiding a collision, but ratherto continue to a standstill, even if the driver lets up the brake pedaland desires an end to the deceleration.

[0033] In FIG. 4 a further traffic situation is illustrated in which themethod according to the present invention is used. A roadway 13 isillustrated which has one lane in each direction of travel. Vehicle 14,which is equipped with the device according to the present invention, avehicle 15 driving in front of this vehicle, and a vehicle 16, whichapproaches on the opposite lane, are located on these lanes. Themovement directions of the vehicles are indicated by arrows in thefigure. In this figure as well, the surrounding-field sensor system ofvehicle 14 detects the traffic situation in the detection range of thevehicle and analyzes this situation with regard to the risk dimension.If the risk dimension increases, for example, due to strong braking ofvehicle 15 driving ahead or a suddenly appearing obstacle betweenvehicles 14 and 15, the controller of the deceleration means entersstate 2 from state 1, in that the braking means are prepared for adeceleration. If the hazard potential increases in the further course ofthis situation or the driver of vehicle 14 initiates deceleration by abrake pedal operation, using which a collision is to be avoided, thecontroller of the deceleration means enters state 3 from state 2, asshown in FIG. 1, or enters state 8 or 3 from state 2, as shown in FIG.2. As a consequence of this strong deceleration, the wheels of vehicle14 may lose road-surface adhesion. Furthermore, it is conceivable thatthe driver of vehicle 14 wishes to perform an avoidance maneuver througha steering intervention and therefore turns the steerable front wheels.In this case, if the decelerated wheels regained road-surface adhesion,the vehicle would abruptly continue the movement direction in thedirection of dashed arrow 20 as a consequence of the steeringdeflection. In the case of an approaching vehicle 16, this would end ina collision with this vehicle. In order to avoid this, thesurrounding-field sensor system of vehicle 14 observes the currentdriving events and evaluates the situation for continued decelerationusing a first risk dimension and for an aborted braking situation usinga second risk dimension. In this case, the second risk dimension wouldbe greater than the first, since a collision would be unavoidable in theevent of an abort of the deceleration operation. In this case, thecontroller of the deceleration means would continue the brakingoperation, even if the driver indicated a desire for abortingdeceleration by letting off the brake pedal. However, a trafficsituation is also conceivable, using braking to avoid a collision, inwhich the driver maintains the brake pedal operation, through which asecond risk dimension would arise which would be greater than the firstrisk dimension of continued emergency braking. In this case, thecontroller of the deceleration means would abort the braking operation,even if the driver continued to operate the brake pedal. The driver thusintuitively receives the possibility of performing an avoidancemaneuver, whose risk dimension would lie below a continued brakingoperation. The controller of the deceleration means therefore has thepossibility of independently deciding whether it is more favorable incase of an imminent collision to continue the deceleration, in order tofurther reduce a possible collision speed, or whether it would be moreadvantageous to abort the deceleration and open the possibility of anavoidance maneuver to the driver. In particular in vehicles which arenot equipped with electronic driving dynamics controllers, this methodoffers an increase in the driving safety.

[0034] The schematic construction of the device according to the presentinvention for performing the method according to the present inventionis sketched in FIG. 5. In a control unit 21 for controlling thedeceleration means, an input field 22 is provided, among other things.This input field 22 receives signals 24 to 26 from various sensors 23 to25. Sensors 23 to 25 may be one or more of the following devices: yawrate sensor, radar sensor, lidar sensor, video sensor, wheel speedsensor, steering angle sensor, accelerator pedal sensor, brake pedalsensor, and mass inertia sensor. Signals 24 to 26 provided by thesesensors are relayed to input field 22, from where they are supplied toan analysis device 27 using a data exchange system 28. This analysis 25device 27 may be a microprocessor or an ASIC. The movement trajectoriesof the stationary or moving obstacles detected by at least one ofsensors 23 to 25 are precalculated on the basis of driving dynamicsmodels in this analysis device 27. Using these precalculated movementtrajectories, a first risk dimension for continued deceleration and asecond risk dimension for aborted deceleration may be determined. Bycomparing these two risk dimensions, analysis device 27 decides whetherthe deceleration is to be continued or aborted. Depending on the resultof the decision, a signal 31 which controls deceleration means 30 issupplied via data exchange device 28 to output field 29.

What is claimed is:
 1. A method for automatically controlling thedeceleration devices (30) of a vehicle (14) during automated braking,wherein, before and during automated braking of the vehicle, thesurrounding-field situation and the particular situation are detectedusing detection devices (23, 25); a first risk dimension for continueddeceleration of the vehicle and a second risk dimension for unbrakedfurther movement of the vehicle are determined on the basis of thesituations detected; and it is decided from a comparison of the firstrisk dimension with the second risk dimension whether the decelerationdevices (30) remain activated or are deactivated.
 2. The method asrecited in claim 1, wherein the automated braking is an automaticallycontrolled deceleration to avoid a collision or to reduce the collisionspeed.
 3. The method as recited in one of claims 1 or 2, wherein thedeceleration means (30) are deactivated during a braking operation ifthe comparison of the risk dimensions shows that the first riskdimension is greater than the second risk dimension.
 4. The method asrecited in one of the preceding claims, wherein the first and the secondrisk dimensions are determined using precalculated movement trajectoriesof the detected obstacles.
 5. The method as recited in one of thepreceding claims, wherein, to precalculate the movement trajectories,the positions and the movements of the particular vehicle (14) and thestationary or moving obstacles (15, 16) in the area surrounding thevehicle are taken into consideration using driving dynamics models. 6.The method as recited in one of the preceding claims, wherein thecharacteristic driving behavior of the driver is taken intoconsideration in establishing the particular situation.
 7. The method asrecited in one of the preceding claims, wherein signals from at leastone of the sensors including yaw rate sensor, radar sensor, lidarsensor, video sensor, wheel speed sensor, steering angle sensor,accelerator pedal sensor, brake pedal sensor, and mass inertia sensorare processed to detect the surrounding-field situation and theparticular situation.
 8. The method as recited in one of the precedingclaims, wherein the controller of the deceleration means has at leastthree states, in particular, the controller of the deceleration meanscan assume the following states no deceleration of the vehicle and nodeceleration preparation; no deceleration of the vehicle, butpreparation of the deceleration means by prefilling the braking systemand applying the brake linings to the brake disks, and maximum possibledeceleration of the vehicle.
 9. The method as recited in one of thepreceding claims, wherein the controller of the deceleration means hasat least four states; in particular, the controller of the decelerationmeans can assume the following states: no deceleration of the vehicleand no deceleration preparation; no deceleration of the vehicle, butpreparation of the deceleration means by prefilling the braking systemand applying the brake linings to the brake disks, deceleration of thevehicle which lies below the maximum possible deceleration of thevehicle, and maximum possible deceleration of the vehicle.
 10. A devicefor automatically controlling the deceleration devices of a vehicle,wherein detection means (23, 25) are provided for detecting thesurrounding-field situation, the vehicle situation, and the driveractivities; these are supplied to an analysis device (27), in whichprobable movement trajectories are established using driving dynamicsmodels; a first and a second risk dimension are established from thesemovement trajectories;, and means (30) are provided for decelerating thevehicle, which are activated or deactivated as a function of the resultof the comparison of the first and the second risk dimensions.
 11. Thedevice as recited in claim 10, wherein the deceleration is a brakingoperation to avoid a collision or to reduce the collision speed.